High efficiency and high capacity glass-free fuel filtration media and fuel filters and methods employing the same

ABSTRACT

High efficiency and high capacity glass-free filtration media include a blend of synthetic non-fibrillated staple fibers and fibrillated cellulosic staple fibers, wherein the fibrillated cellulosic fibers are present in the media in an amount to achieve an overall filtration efficiency at 4 microns of 95% or higher and a ratio of filtration capacity to media caliper of 0.5 mg/in 2 /mils and greater. The filtration media is made by forming a wet laid sheet from a fibrous slurry blend of the synthetic non-fibrillated staple fibers and fibrillated cellulosic staple fibers, followed by drying the sheet to obtain the filtration media. Optionally, the filtration media may be provided with a resin binder and may be grooved and/or pleated.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of commonly owned U.S. application Ser.No. 13/417,022 filed on Mar. 9, 2012 (now U.S. Pat. No. 9,662,600), theentire content of which is expressly incorporated hereinto by reference.

FIELD

The embodiments disclosed herein relate generally to high efficiency andhigh capacity glass-free fuel filtration media and to fuel filters andmethods of filtering fuel which employ the same.

BACKGROUND

Filtration media possessing high filtration efficiency of small sizedparticulates generally requires small pores in the media so that theparticulates to be filtered cannot pass through the media. Small poresin a media however generally result in low permeability and thereforecause high fluid pressure drop through the media. When particulates arecaptured physically on the upstream side of the media, they will overtime gradually block the pores of the media which in turn cause thefluid pressure drop across the media to gradually increase. The qualityof any filtration media is thus characterized by the amount ofparticulates that are capable of being captured (also known as “mediacapacity”), which occurs at a specific predetermined pressure drop. Ifthe specific predetermined pressure is reached too rapidly, theresulting media capacity will thus be low. The general rule in thefiltration industry is that the higher the efficiency possessed by afiltration media, the lower its capacity. Oftentimes therefore acompromise is needed to achieve both acceptable filtration mediaefficiency and capacity.

High efficiency filtration media, such as required for fuel filtration,often contain staple glass microfibers. Glass microfibers possess uniquefiltration properties due to their needle-like fiber shape, rigidity andsmall size. Glass microfibers are therefore widely used in conventionalfiltration media to provide both high efficiency and high capacity.

With increasing process pressure, for example during heavy-duty dieselfuel filtration, concerns have risen that glass microfibers could bewashed out from the filtration media with the filtered fuel and thusenter and damage the internal combustion engine. In order to preventproblems that could result from glass microfibers leaching out of thefiltration media, efforts haven been made to develop high-efficiency andhigh capacity glass-free alternatives to glass microfiber-containingmedia. The leaching of glass microfibers into the downstream filtrate isnot only of concern for internal combustion engine fuel filtration, butalso for example in any kind of filtration that comes in contact withthe human body, e.g. through ingestion.

Conventional commercially available glass-free filtration media oftencontain a base-media that provides the required filtration efficiency,e.g. from 100% wood pulp, and a laminated layer of fine staple fibersthat provides the required filtration capacity. The manufacture of theseconventional forms of filtration media requires high-pressure nipping ofthe media as well as a multi-stage manufacturing process including thelamination of the efficiency and the capacity layers, resulting inoverall high production cost. The multi-layer structure of theseconventional media often also results in relatively higher thickness,which is disadvantageous for the pleat geometry of the resulting filter.

It would therefore be highly desirable if filtration media could beprovided which is glass-free (i.e., does not contain any glass fibers)but yet exhibits high filtration capacity and efficiency. Suchfiltration media should also posses a minimum strength sufficient to befurther processed and/or pleated (e.g., so as to allow for the formationof filter units comprising such media). It is therefore towardsfulfilling such desirable attributes that the present invention isdirected.

SUMMARY OF EXEMPLARY EMBODIMENTS

According to one aspect, the embodiments disclosed herein provide forglass-free non-woven filtration media which is comprised of a blend ofstaple synthetic fibers and fibrillated cellulosic fibers. According tocertain embodiments, the staple synthetic fibers will most preferablycomprise or consist of synthetic microfibers. Optionally, the filtrationmedia of certain other embodiments may contain non-fibrillatedcellulosic fibers in an amount which does not significantly adverselyaffect the filtration efficiency and/or capacity of the media.

Certain embodiments will be in the form of high efficiency and highcapacity glass-free non-woven filtration media comprising a blend ofsynthetic non-fibrillated staple fibers and fibrillated cellulosicstaple fibers, wherein the fibrillated cellulosic fibers are present inthe media in an amount to achieve an overall filtration efficiency at 4microns of about 95% or higher and a ratio of filtration capacity tomedia caliper of 0.5 mg/in²/mils and greater.

The synthetic non-fibrillated stable fibers may be formed of athermoplastic polymer selected from the group consisting of polyesters,polyalkylenes, poyacrylonitriles, and polyamides. Polyesters, especiallypolyalkylene terephthalates, are especially desirable. Some embodimentswill include non-fibrillated polyethylene terephthalate (PET) stablemicrofibers having an average fiber diameter of less than about 10microns and an average length of less than about 25 millimeters. Thesynthetic staple fibers may be present in an amount between about 50 wt.% to about 99.5 wt. % ODW.

The fibrillated cellulosic staple fibers may comprise fibrillatedlyocell nanofibers. Certain embodiments will include fibrillated lyocellnanofibers in an amount of between about 0.5 to about 50 wt. % ODW. Thefibrillated cellulosic staple fibers may possess a Canadian StandardFreeness (CSF) of about 300 mL or less.

Certain embodiments will include a blend of staple polyethyleneterephthalate microfibers having an average fiber diameter of less thanabout 10 microns and an average length of less than about 25 millimeterswhich are present in an amount of between about 50 wt. % to about 99.5wt. % ODW, and fibrillated lyocell staple fibers having a CanadianStandard Freeness (CSF) of about 300 mL or less which are present in anamount of at least about 0.5 to about 50 wt. % ODW. The fibrillatedcellulosic fibers may have an average diameter of about 1000 nanometersor less and an average length between about 1 mm to about 8 mm.

Other components and/or additives may be incorporated into thefiltration media. By way of example, some embodiments may includenatural wood pulp blended with the synthetic non-fibrillated staplefibers and fibrillated cellulosic staple fibers. If employed, thenatural wood pulp may be present in an amount of about 25 wt. % ODW orless. Wet strength additives, optical brighteners, fiber retentionagents, colorants, fuel-water separation aides (e.g., silicone additivesand associated catalyzers), water or oil repellants (e.g.,fluorocarbons), fire or flame retardants, and the like may also beemployed as may be desired.

Resin binders may also be added to the filtration media to achievedesired physical properties. If employed, such binder resins may bepresent in an amount between about 2 to about 50 wt. % SDC.

The filtration media may be formed by a wet-laid slurry process. By wayof example, the filtration media may be made by forming a wet laid sheetfrom a fibrous slurry comprised of a blend of synthetic non-fibrillatedstaple fibers and fibrillated cellulosic staple fibers, and drying thesheet to obtain the filtration media. The filtration media may begrooved and/or pleated so as to facilitate its use in filtration devices(e.g., filter units associated with on-board fuel filtration systems).

These and other attributes of the various embodiments according to theinvention will be better understood by reference to the followingdetailed descriptions thereof.

BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS

FIG. 1 is a plot of multipass (MP) efficiency (%) at 4 microns versusthe content of fibrillated Lyocell nanofibers (wt. %) present in thefiltration media.

DEFINITIONS

As used herein and in the accompanying claims, the terms below areintended to have the definitions as follows.

“Fiber” is a fibrous or filamentary structure having a high aspect ratioof length to diameter.

“Staple fiber” means a fiber which naturally possesses or has been cutor further processed to definite, relatively short, segments orindividual lengths.

“Nanofibers” mean fibers having an average diameter of less than about1000 nanometers.

“Fibrous” means a material that is composed predominantly of fiberand/or staple fiber.

“Non-woven” means a collection of fibers and/or staple fibers in a webor mat which are randomly interlocked, entangled and/or bound to oneanother so as to form a self-supporting structural element.

“Synthetic fiber” and/or “man-made fiber” refers to chemically producedfiber made from fiber-forming substances including polymers synthesizedfrom chemical compounds and modified or transformed natural polymer.Such fibers may be produced by conventional melt-spinning, solution- orsolvent-spinning and like filament production techniques.

A “cellulosic fiber” is a fiber composed of or derived from cellulose.

“Freeness” is the measure, in mL, of the rate in which a dilutesuspension of staple fiber may be drained, as described in TAPPI

Canadian standard method T 227 om-94 (1994) (hereinafter sometimesreferred to as “Canadian Standard Freeness” or “CSF”), the entirecontent of which is expressly incorporated hereinto by reference.

“Fibrils” are tiny, minute irregular threadlike elements associated witha staple fiber.

“Fibrillated” means staple fibers that have been further acted upon toform numerous fibrils and which exhibit a Canadian Standard Freeness ofabout 300 mL or less, preferably about 200 mL or less, typically betweenabout 10 to about 200 mL.

“Non-fibrillated” means unprocessed staple fibers having essentially nofibrils and which exhibit a Canadian Standard Freeness of greater thanabout 500 mL.

“Fibrillatable” means non-fibrillated staple fibers that inherentlypossess the ability to be fibrillated using standard mechanical beaters,refiners and the like employed in the paper-making industry.

“Oven-dry weight” or “ODW” means the total weight of fibers or fabricafter drying in a hot air oven at 350° F. (177° C.) for 5 minutes.

“Saturated dry cured” or “SDC” means a media saturated with resin,air-dried or dried at low heat for a time sufficient to evaporatesolvent from the resin and cured in a hot air oven at 350° F. (177° C.)for 5 minutes.

DETAILED DESCRIPTION

A. Non-Fibrillated Staple Synthetic Fibers

Virtually any conventional synthetic non-fibrillated staple fibers maybe employed in the filtration media of this invention. Especiallypreferred embodiments will include synthetic non-fibrillated staplefibers formed of a thermoplastic polymer, such as polyesters (e.g.,polyalkylene terephthalates such as polyethylene terephthalate (PET),polybutylene terephthalate (PBT) and the like), polyalkylenes (e.g.,polyethylenes, polypropylenes and the like), poyacrylonitriles (PAN),and polyamides (nylons, for example, nylon-6, nylon 6,6, nylon-6,12, andthe like). Preferred are staple PET fibers.

The synthetic staple fibers are most preferably microfibers, that isstaple fibers which possess average fiber diameters of less than about10 microns, sometimes less than about 8 microns or even less than about5 microns, and lengths of less than about 25 millimeters, sometimes lessthan about 10 millimeters, such as less than about 6.5 millimeters(e.g., less than about 3.5 millimeters).

Particularly preferred synthetic staple microfibers are waterdispersible polyalkylene terephthalate microfibers. Preferred are staplepolyethylene terephthalate (PET) microfibers. In certain preferredembodiments, the staple PET microfibers are the result of water-washingof water non-dispersible sulfopolyester fibers having a glass transitiontemperature (Tg) of at least 25° C., the sulfopolyester comprising: (i)about 50 to about 96 mole % of one or more residues of isophthalic acidor terephthalic acid; (ii) about 4 to about 30 mole %, based on thetotal acid residues, of a residue of sodiosulfoisophthalic acid; (iii)one or more diol residues wherein at least 25 mole %, based on the totaldiol residues, is a poly(ethylene glycol) having a structureH—(OCH₂—CH₂)_(n)—OH, wherein n is an integer in the range of 2 to about500; and (iv) 0 to about 20 mole %, based on the total repeating unites,of residues of a branching monomer having 3 or more hydroxyl, and/orcarboxyl functional groups. These preferred synthetic staple PETmicrofibers and their methods of production are more fully described inUS Published Patent Application Nos. 2008/0311815 and 2011/0168625 (theentire content of each being expressly incorporated hereinto byreference) and are commercially available from Eastman Chemical Company,Kingsport, Tenn.

The synthetic staple fibers will be employed in the filtration media inan amount between about 50 wt. % to about 99.5 wt. % ODW, preferablybetween 75 wt. % to about 97.5 wt. % ODW. Especially preferredembodiments will include the synthetic staple fibers in an amountbetween about 80 wt. % to about 90 wt. % ODW.

B. Cellulosic Fibers

The filtration media will necessarily include fibrillated cellulosicstaple fibers which possess a Canadian Standard Freeness (CSF) of about300 mL or less, preferably about 200 mL or less, typically between about10 to about 200 mL.

Preferred fibrillatable cellulosic staple fibers are those made bydirect dissociation and spinning of wood pulp in an organic solvent,such as an amine oxide, and are known as lyocell staple fibers. Thefibrillatable cellulose staple fibers may thus be fibrillated by beingsubjected to standard mechanical beaters, refiners and the like employedin the paper-making industry.

The fibrillated cellulosic staple fibers will be employed in thefiltration media in an amount between about 0.5 to about 50 wt. % ODW,preferably between 2.5 to about 25 wt. % ODW. Especially preferredembodiments will include the fibrillated cellulosic staple fibers in anamount between about 10 to about 20 wt. % ODW.

Especially preferred fibrillated cellulosic staple fibers includelyocell staple fibers. The lyocell staple fibers are most preferablynanofibers, that is staple fibers having an average diameter of about1000 nanometers or less, or sometimes about 400 nanometers or less, forexample about 100 nanometers. Some especially preferred embodiments willinclude fibrillated cellulosic staple fibers of about 250 nanometers.The average length of the Lyocell staple nanofibers is typically betweenabout 1 mm to about 8 mm, or between about 2 mm to about 6 mm, or about3 mm to about 4 mm.

Preferred fibrillated lyocell nanofibers are commercially available fromEngineered Fibers Technology, LLC under the tradename EFTec™Nanofibrillated Fibers. Preferred commercially available forms of thefibrillated lyocell nanofibers include EFTec™ L010-4, L040-4 and L200-6Nanofibrillated fibers having degrees of fibrillation at 4 mm or 6 mmfiber length of ≤10 CSF, 40 CSF and 200 CSF, respectively.

Other non-fibrillated cellulosic staple fibers may optionally be blendedwith the non-fibrillated synthetic staple fibers and the fibrillatedcellulosic staple fibers so as to impart additional stiffness to thefiltration media. According to some embodiments, therefore, the additionof from 0 up to about 25 wt. % ODW, for example, from 0 wt. % to about20 wt. % ODW or to about 15 wt. % ODW, of natural wood pulp(non-lyocell) staple fibers may be desired. A variety of non-lyocellnon-fibrillated cellulosic staple fibers are commercially available andmay be blended with the other components of the filter media disclosedherein as may be desired.

C. Other Components

The filtration media according to certain embodiments may include aresin binder to achieve desired physical properties. Any suitable resinbinders may be added to the filtration media for such a purpose.Suitable examples of binder resins that may optionally be employedinclude polymers such as styrene acrylic, acrylic, polyethylene vinylchloride, styrene butadiene rubber, polystyrene acrylate, polyacrylates,polyvinyl chloride, polynitriles, polyvinyl acetate, polyvinyl alcoholderivates, starch polymers, epoxy, phenolics and combinations thereof,including both waterborne or solvent versions. In some cases, the binderresin may be in the form of a latex, such as a water-based emulsion.

If employed, the resin binder may be present in amounts between about 2to about 50 wt. % SDC, preferably between 10 to about 30 wt. % SDC.Especially preferred embodiments will include the resin binder in anamount between about 12 to about 25 wt. % SDC.

Preferred resin binders include phenolic resins, acrylic resins (e.g.,vinyl acrylic latex resins), melamine resins, silicone resins, epoxyresins and the like. One phenolic (phenolformaldehyde) resin that may beemployed includes DURITE® SL161A commercially available from MomentiveSpecialty Chemicals Inc. of Louisville, Ky. One suitable latex basedresin binder that may be employed is PD 0458 M1 (a polyoxymethylenenonylphenol branched ether phosphate dispersed in formaldehyde)commercially available from HB Fuller Co. of St. Paul, Minn. A suitablemelamine binder resin may be ASTRO® Celrez PA-70 methylated melamineresin system commercially available from Momentive Specialty ChemicalsInc. of Louisville, Ky. Suitable acrylic resins include ACRODUR®formaldehyde-free water-based acrylic resins commercially available fromBASF Corporation.

The filtration media may also contain additives conventionally employedin wet-laid filtration media, such as for example, wet strengthadditives, optical brighteners, fiber retention agents, colorants,fuel-water separation aides (e.g., silicone additives and associatedcatalyzers), water or oil repellants (e.g., fluorocarbons), fire orflame retardants, and the like. If present, these additives may beincluded in amounts of up to about 20 wt. % ODW, preferably up to about10 wt. % ODW, for example between about 1 to about 10 wt. %.

D. Methods of Making

The filtration media described herein may be made by any conventional“wet-laid” paper-making technology. Thus, for example, predeterminedamounts of the non-fibrillated synthetic staple fibers and thefibrillated cellulosic staple fibers (along with any optionalcomponents, such as the natural wood pulp fibers and/or additives) andwater may be placed in a pulper or beater. The fibers are mixed anddispersed by the pulper or beater evenly in the water to form a slurrybatch. Some mechanical work can also be performed on the fibers toaffect physical parameters, such as permeability, surface properties andfiber structure. The slurry batch may thereafter be transferred to amixing chest where additional water is added and the fibers arehomogenously blended. The blended slurry may then be transferred to amachine chest where one or more slurry batches can be combined, allowingfor a transfer from a batch to a continuous process. Slurry consistencyis defined and maintained by agitation to assure even dispersion offibers. In this regard, the slurry may optionally be passed through arefiner to adjust physical parameters.

The slurry is then transferred to a moving wire screen where water isremoved by means of gravity and suction. As water is removed, the fibersform into a fibrous nonwoven mat or sheet having characteristicsdetermined by a number of process variables, including for example, theslurry flow rate, machine speed, and drainage parameters. The formedsheet may optionally be compressed while still wet so as to compact thepaper and/or modify its surface characteristics. The wet paper mat isthen moved through a drying section comprised of heated rollers (or“cans” in art parlance) where most of the remaining entrained water isremoved. The dried web may then have a binder applied by anyconventional means, such as dipping, spray coating, roller (gravure)application and the like. Heat may then subsequently be applied to drythe web.

If employed as a pleated filtration media, the dried web mayadvantageously be subjected to machine-direction (longitudinal) groovingusing mated male/female rollers. If employed, the media may have about50 longitudinally extending grooves per 200 mm of media width. Eachgroove will thus preferably have a nominal width of about 4 mm. Atypical grooved glass-containing high-efficiency fuel grade hasdimensions such as overall SD (saturated and dried, but not cured)caliper of about 38 mils, SD groove depth of about 13 mils, and SDoptical caliper A (optical measurement of media thickness in one groove,therefore representing corresponding flat thickness) of about 28 mils.

The finished (optionally grooved) filtration media may then be taken upon a roll for further processing into finished filter products. Forexample, one or more finished filtration media sheets may be laminatedwith one or more other sheets of material (e.g., at least one additionalfiltration media layer, supporting layer and the like) to achievedesired physical and performance characteristics. The filtration mediamay also be pleated and formed into a cylindrical filter cartridge thatmay then be provided as a component part of a filtration unit (e.g., anon-board fuel filter unit). Co-pleating of the filtration media with asupporting wire mesh layer may be desirable in certain end useapplications.

The basis weight of the finished filtration media is not critical. Thus,the finished filtration media may have a basis weight of at least about15 grams per square meter (gsm), more preferably at least about 35 gsmup to about 300 gsm. Some embodiments of the filtration media maypossess a basis weight of between about 50 up to about 200 gsm.

The present invention will be further illustrated by the followingnon-limiting examples thereof.

EXAMPLES Example 1

In the examples described below, the following components were employed:

-   -   PET Microfibers: Non-fibrillated PET staple microfibers having        an average diameter of 2.5 microns, commercially available from        Eastman Chemical Company,    -   Fibrillated Lyocell: Fibrillated lyocell nanofibers commercially        available from Engineered Fibers Technology LLC under the        tradename EFTec™ fibers with Lyocell L010 having a CSF of ≤10        mL; Lyocell L040 having a CSF of 40 mL; and Lyocell L200 having        a CSF of 200 mL.    -   Sodra Red: Chemi-Thermal-Mechanical (CTM) Softwood pulp with a        Freeness of 600-700 ml and SR of 15, and a pH of 7.5,        manufactured by Södra, Sweden. Bulk is 4 cm3/g.    -   Alabama Pine or Alabama River Softwood: Southern Softwood        elemental chlorine free (ECF) Kraft Pulp manufactured by        Georgia-Pacific, USA with CSF ranges from 300 to 740 ml and bulk        of 1.48-2.1 cm³/g.    -   HPZIII: Mercerized southern softwood from Buckeye Technologies,        Inc. having an average fiber length of 1.8 mm and 7.3 cm³/g bulk    -   GRAND PRAIRIE: Northern softwood from Weyerhaeuser Co. having        average fiber length of 2.3 mm, CSF ranges from 648-300, bulk        ranges from 1.52-1.24 cm³/g.    -   FIBRIA: Fibria ECF Bleached Eucalyptus Pulp from Aracruz        Cellulose (USA) Incorporated having a drainability of 22-55 SR        and a fiber length of about 0.70 mm    -   KYMENE: A wet strength additive consisting of 12-13% solids of        an aqueous solution of a cationic amine polymer-epichlorohydrin        adduct having specific gravity is 1.03, pH is 3.5-4.5 and the        solution contains 12-13% solids.    -   MOMENTIVE 161A: EPON™ Resin 161, a multifunctional epoxidized        phenolic novolac resin binder commercially available from        Momentive Specialty Chemicals, Inc. and having a epoxide        equivalent weight of 169-178 g/eq (ASTM D1652), a viscosity (25°        C.) of 18,000-28,000 cP (ASTM D2196) and a density (25° C.) of        10.0 lb/gal.        Procedure:

The samples were produced using a laboratory wetlaid hand sheet mold.The furnish as described in the recipe was mixed with 2 liters of tapwater and disintegrated with a standard laboratory disintegrator (Noram)for 1500 revolutions. The furnish was then poured into the wetlaid moldand diluted with approx. 25 liters of tap water, stirred 3 times with apedal stir, and drained through a standard paper machine wire.

The hand sheets were then squeezed dry with a couching roller rolledacross 3 times, pre-dried in a flat bed speed oven for 5 minutes at 350°F. and subsequently dried in an oven for 5 minutes at 350° F. Rawphysical data such as raw basis weight, caliper, air permeability weretaken immediately after oven drying.

The samples were then saturated with a standard phenolic resin (161Afrom Momentive Specialty Chemicals, Inc.) at a content of 16% (bathsolids of resin bath were 18% in methanol as solvent). The samples werethen air dried for 24 hours in ambient conditions, and cured to arriveat the SDC (saturated dried cured) level at 350° F. for 5 minutes. SDCbasis weight was recorded immediately after curing, and other SDC datasuch as SDC caliper and SDC air permeability were measured subsequently.Specifically, these physical parameters were measured as follows:

SDC Caliper: The caliper (thickness) of SDC media was measured using a89-100 Thickness Tester from Thwing-Albert Instrument Company accordingto TAPPI Standard T411, “Thickness (caliper) of paper, paperboard andcombined board” (incorporated fully by reference herein).

SDC Air Permeability: The air permeability of SDC media was tested witha FX3300 LabAir IV Air Permeability Tester from TexTest, according toASTM D737, “Standard Test Method for Air Permeability of TextileFabrics” incorporated fully by reference herein). Measurements wererecorded at 125 Pa in Cubic Feet per Minute (cfm) per area of one squarefoot.

Filtration performance was measured using a multipass (MP) testaccording to ISO 19438:2003, “Diesel fuel and petrol filters forinternal combustion engines—Filtration efficiency using particlecounting and contaminant retention capacity” (incorporated hereinto byreference). ISO 19438:2003 specifies a multi-pass filtration test, withcontinuous contaminant injection using the on-line particle countingmethod, for evaluating the performance of fuel filters for internalcombustion engines submitted to a constant flow rate of test liquid. Thetest procedure determines the contaminant capacity of a filter, itsparticulate removal characteristics and differential pressure. ISO19438:2003 is applicable to filter elements having a rated flow ofbetween 50 I/h and 800 l/h; however, by agreement between filtermanufacturer and customer, and with some modification, the procedure ispermitted for application to fuel filters with higher flow rates. Theparameters employed in the MP Test are:

-   -   Test dust used: ISO Fine    -   Flow rate: 1.89 liter/min    -   Oil viscosity: 15 mm²/s @ 43° C.=109° F.    -   Injection gravimetric: 75.7 mg/liter    -   BUGL (Basic Upstream Gravimetric Level): 10 mg/liter

Hand sheets were made using 2.5 micron PET microfiber (Eastman ChemicalCompany), different grades of fibrillated lyocell (Grades L010, L040,L200 from Engineered Fibers Technology, LLC), and three different typesof wood pulp. Most hand sheets also contained Kymene, a wet strengthadditive, to imitate production conditions, in amounts noted in thetables below.

The “Capacity/Caliper Ratio” was calculated by dividing the mediacapacity (mg/int) by the media caliper (mils) in order to normalize thecapacity data to account for different sheet caliper thickness. “Overallefficiency at 4 microns” was determined using the multipass (MP)filtration test described previously.

TABLE 1 Physical Properties- Composition Saturated, Multipass Normal-Furnish Composition Resin Dried, Cured Performance ized % PET OverallSDC Ap- Overall Ca- Micro- % Air parent Effi- pacity: = fiber PhenolicPerme- Ca- ciency Capacity/ Eastman % Wet Resin SDC ability pacity @ 4Caliper PET % Fibrillated Strength Mo- Basis SDC [cfm] [mg/in²] mi- [mg/Hand Micro- Lyocell Additive mentive Weight Caliper @ [mg/ crons inch2/Sheets fiber L1010 L040 L200 Kymene 161A [g/m2] [mils] 125 Pa inch2] %mils] 61 84 16 1.0 16.9 111 19.3 2.37 18.3 99.8 0.95 30 86 14 1.0 16.7111 20.2 2.77 21.3 99.8 1.05 52 94 6 1.0 16.3 110 18.2 3.04 17.7 99.20.97 32 89 11 1.0 16.8 111 24.9 3.36 20.1 99.5 0.81 63 97 3 1.0 13.7 10816.7 3.62 21.1 99.0 1.26 4 85 15 1.0 16.2 139 33.0 2.60 21.3 98.8 0.6429 93 7 1.0 17.7 141 27.4 2.74 21.1 99.4 0.77 34 93 7 1.0 16.8 140 25.33.00 20.7 99.2 0.82 39 95 5 1.0 17.5 141 30.9 3.45 21.9 99.2 0.71 50 1000 1.0 17.3 141 29.6 3.70 21.0 97.9 0.71 26 90 10 1.0 16.7 175 34.0 2.4922.2 99.7 0.65 59 94 6 1.0 17.4 176 39.0 2.70 21.3 99.4 0.55 54 100 01.0 17.2 176 31.9 2.98 21.9 98.9 0.69 58 75 25 1.0 17.8 112 27.0 2.3219.4 99.9 0.72 60 77 23 1.0 18.1 112 24.9 2.58 19.0 99.8 0.76 44 81 191.0 16.6 111 31.2 3.00 23.5 99.8 0.75 38 85 15 1.0 16.9 111 27.6 3.1721.7 99.7 0.79 18 85 15 1.0 17.9 112 26.8 3.39 24.5 99.6 0.92 20 85 151.0 16.7 111 30.3 3.41 25.4 99.7 0.84 56 83 17 1.0 18.6 142 30.7 2.4820.1 99.8 0.65 64 85 15 1.0 14.1 137 37.3 2.76 20.8 99.7 0.56 10 91 91.0 17.2 141 33.4 3.03 22.0 99.4 0.66 7 87 13 1.0 16.7 140 39.5 3.3722.4 99.6 0.57 24 92 8 1.0 17.7 141 38.3 3.38 25.5 99.3 0.67 27 90 101.0 19.1 179 42.5 2.74 24.9 99.6 0.59 43 91 9 1.0 16.8 175 43.2 3.0424.3 99.5 0.56 42 93 7 1.0 18.2 177 44.6 3.21 26.6 99.3 0.60 53 98 2 1.018.8 178 42.2 3.25 22.5 98.4 0.53 57 98 2 1.0 21.3 182 40.3 3.39 21.898.8 0.54 33 89 11 0.3 15.7 190 30.9 2.08 26.7 99.9 0.87 36 92 8 0.315.9 189 31.4 2.40 25.8 99.8 0.82 39 97 3 0.3 15.2 185 29.9 2.92 26.599.3 0.89 40 100 0 0.3 15.5 157 29.6 3.20 24.2 98.7 0.82 70 30 0.3 13.852 7.4 2.48 20.6 99.9 2.78 60 40 0.3 12.8 53 8.9 1.96 19.5 100.0 2.20 982 0.3 14.6 190 29.1 2.83 26.7 99.9 0.92 90 10 0.3 14.4 189 27.3 1.8627.3 99.9 1.00 41 89 11 0.3 16.9 189 33.9 2.99 25.8 99.2 0.76 43 75 250.3 16.1 187 33.4 2.80 17.8 99.5 0.53 45 50 50 0.3 16.9 185 31.6 2.1820.7 99.9 0.65 46 95 5 0.3 15.3 186 29.2 2.63 23.1 99.5 0.79 47 92 8 0.315.3 186 36.0 2.45 23.0 99.8 0.64 48 89 11 0.3 17.0 189 33.9 2.05 23.199.9 0.68

The data in Table 1 above demonstrate that filtration media formed ofPET microfibers and fibrillated lyocell microfibers exhibited anadvantageous capacity/caliper ratio of 0.5 mg/in²/mils and greater atapproximately 98% efficiency at 4 microns or higher.

Example 2

Example 1 was repeated except that filtration media was formed on astandard Fourdrinier wet-laid paper line. The results of these trialsare shown in Table 2 below.

TABLE 2 Composition Multi pass Furnish Resin Physical Properties-Performance Normalized Composition Overall % Saturated, Dried, CuredOverall Capacity: = % PET % % Wet Phenolic SDC SDC Air ApparentEfficiency Capacity/ Microfiber Fibrillated Strength Resin Basis SDCPermeability Capacity @ 4 Caliper Roll 2.5 Lyocell Additive MomentiveWeight Caliper [cfm] @ [mg/in²] microns [mg/inch2/ Sample microns L010-4Kymene 161A [g/m2] [mils] 125 Pa [mg/inch2] [%] mils]  1A 84 16 0.1 17139 18.4 2.58 17.0 98.4 0.92  2A 84 16 0.1 17 145 19.0 2.76 16.4 97.60.86  3A 84 16 0.1 17 115 18.1 3.37 16.9 97.4 0.93  4B 84 16 0.1 17  9614.5 4.73 18.2 94.2 1.26  7A 86 14 0.1 17 151 16.7 1.96 18.0 99.6 1.08 8B 86 14 0.1 17 180 21.2 1.54 15.1 99.9 0.71  9B 86 14 0.1 17 177 22.91.58 17.0 99.8 0.74 10B 86 14 0.1 17 198 24.8 1.42 14.1 99.9 0.57 11A 8911 0.1 17 139 18.0 3.33 21.3 97.6 1.18 12B 89 11 0.1 17 125 16.8 3.9620.8 94.9 1.24 13B 89 11 0.1 17 174 22.1 2.44 21.2 99.1 0.96 14B 89 110.1 17 144 20.6 3.84 22.5 95.4 1.09

The data in Table 2 above confirms that the capacity/caliper ratio is0.5 mg/in²/mils and greater for all basis weights, even though the ratiotends to decrease with an increase in basis weight. The data also showsthat the media had acceptable filtration efficiency of 95% or greater at4 microns, typically 97% or greater at 4 microns.

Example 3

Example 1 was repeated with different amounts of natural wood pulpblended with the PET microfibers and fibrillated lyocell microfibers invarying amounts. The data appear in Tables 3A and 3B below.

TABLE 3A Composition Resin Fiber Furnish Composition Overall % % PET % %Wet Phenolic Microfiber Fibrillated % Wood Pulp Strength Resin HandEastman PET Lyocell Sodra Alabama Grand Additive Momentive SheetsMicrofibers L010 Red Pine HPZIII Prairie Fibria Kymene 161A 69 11 20 0.016.0 69 12 19 0.0 16.0 67 16 17 0.0 16.0 1 89 11 0 0.3 15.6 3 84 11 50.3 15.8 5 79 11 10 0.3 16.6 7 74 11 15 0.3 16.0 9 69 11 20 0.3 16.6 1164 11 25 0.3 16.3 13 84 11 5 0.3 16.0 15 79 11 10 0.3 16.7 17 74 11 150.3 16.7 19 69 11 20 0.3 16.9 21 64 11 25 0.3 16.9 23 84 11 5 0.3 18.125 79 11 10 0.3 16.9 27 74 11 15 0.3 16.9 29 69 11 20 0.3 18.9 31 64 1125 0.3 17.2 30 20 50 0.3 13.5 30 5 65 0.3 16.1 30 20 50 0.3 13.9 30 1060 0.3 15.8 30 20 50 0.3 17.4

TABLE 3B Normal- Multipass ized Saturated, Dried, Cured PerformanceCapac- SDC Air Apparent Overall ity: = SDC Perme- Capacity EfficiencyCapacity/ Basis SDC ability [mg/in²] @ 4 Caliper Hand Weight Caliper[cfm] @ [mg/ microns [mg/inch2/ Sheets [g/m2] [mils] 125 Pa inch2] [%]mils] 127 28.0 4.88 19.4 99.5 0.69 124 33.0 5.69 17.8 99.5 0.54 128 27.23.50 20.0 99.7 0.74 1 201 34.6 2.10 22.0 99.8 0.63 3 197 36.4 2.23 21.399.8 0.59 5 201 35.4 2.12 20.3 99.8 0.57 7 199 30.4 1.88 17.0 99.8 0.569 208 38.7 2.07 13.0 99.6 0.33 11 208 35.6 1.78 17.8 99.7 0.50 13 19737.0 2.10 19.2 99.8 0.52 15 200 35.5 2.04 21.8 99.7 0.61 17 203 38.22.13 21.3 99.7 0.56 19 202 33.1 2.12 17.8 99.7 0.54 21 206 35.4 2.2215.1 99.7 0.43 23 211 38.9 2.37 19.9 99.8 0.51 25 207 43.6 2.68 25.499.7 0.58 27 198 35.5 2.72 20.1 99.6 0.57 29 203 37.3 2.89 19.4 99.50.52 31 201 41.7 3.08 20.8 99.3 0.50 189 27.3 1.03 13.0 100.0 0.48 18925.7 2.62 12.0 95.8 0.47 190 34.3 1.57 16.8 100.0 0.49 191 36.0 2.6617.0 99.5 0.47 197 43.5 2.66 21.3 99.9 0.49

The data above demonstrate that the addition of natural wood pulp to ablend of PET nanofibers and fibrillated lyocell deteriorates thecapacity properties of the filtration media. At levels above about 20-25wt. %, the wood pulp can cause the capacity/caliper ratio to decreasebelow 0.5 mg/in²/mils and thus should be avoided.

Example 4

Example 1 was repeated with different amounts of fibrillated lyocell.The data appear in Table 4 below.

TABLE 4 Composition Resin Physical Properties - Fiber Furnish Overall %Saturated, Dried, Cured % Wet Phenolic SDC SDC Air % PET % FibrillatedStrength Resin Basis SDC Permeability Microfiber Lyocell AdditiveMomentive Weight Caliper [cfm] @ Hand Sheets 2.5 microns L010 Kymene161A [g/m2] [mils] 125 Pa 1 100 0 0 19.85 57.76 8.5 8.40 2 97.5 2.5 018.73 56.42 8.4 8.50 3 95 5 0 18.11 55.08 7.0 7.60 4 90 10 0 17.89 56.577.5 5.40 5 85 15 0 15.70 54.04 6.7 4.12 6 80 20 0 17.77 56.12 8.0 4.12 7100 0 0 18.08 110.31 16.0 4.28 8 97.5 2.5 0 17.62 108.97 15.8 4.40 9 955 0 17.66 109.56 16.3 3.89 10 90 10 0 17.28 108.52 15.3 3.58 11 85 15 017.33 109.11 17.7 2.83 12 80 20 0 16.32 107.63 16.7 2.13 13 100 0 019.67 161.22 30.6 3.40 14 97.5 2.5 0 18.67 158.68 24.10 3.10 15 95 5 017.56 158.54 26.75 2.90 16 90 10 0 15.86 160.47 22.80 2.20 17 85 15 017.53 166.43 24.70 1.84 18 80 20 0 17.85 167.62 27.90 1.65 19 100 0 018.14 218.23 40.00 3.13 20 97.5 2.5 0 17.56 221.21 38.68 2.57 21 95 5 016.72 219.87 36.10 2.30 22 90 10 0 16.80 217.04 38.40 1.78 23 85 15 015.49 212.42 34.30 1.45 24 80 20 0 16.84 218.38 32.70 1.28 MultipassPerformance Apparent Overall Efficiency @ Normalized Capacity: =Capacity [mg/in²] 4 microns Capacity/Caliper Hand Sheets [mg/inch2] [%][mg/inch2/mils] 1 21.1 95.3 2.49 2 22.4 95.6 2.68 3 20.1 97.2 2.86 418.4 98.8 2.46 5 14.8 99.6 2.21 6 14.3 99.7 1.79 7 23.7 97.8 1.49 8 23.198.7 1.46 9 22.8 98.9 1.40 10 21.9 99.4 1.44 11 21.1 99.7 1.19 12 20.299.9 1.21 13 25.8 98.4 0.84 14 22.5 99.1 0.93 15 26.4 99.5 0.99 16 17.199.9 0.75 17 19.2 99.9 0.78 18 21.3 100.0 0.77 19 25.9 98.8 0.65 20 24.099.5 0.62 21 18.3 99.7 0.51 22 21.9 99.9 0.57 23 17.1 99.9 0.50 24 17.999.9 0.55

The data in Table 4 above show that fibrillated lyocell staple fiberswhen added in a relatively small amount (e.g, about 2.5 wt. % or more)to PET microfibers increases the filtration efficiency of the media.This is further shown by the graph of FIG. 1. Specifically, FIG. 1 showsthat at 2.5 wt. % fibrillated lyocell, increased filtration efficienciesacross all basis weights of the filtration media ensue. Thus, for higherbasis weight media, amounts of fibrillated lyocell less than 2.5 wt. %may be present in order to achieve filtration efficiency of about 98% orgreater.

The data also show that, although the relative amounts of the PETnanofibers and fibrillated lyocell nanofibers can be varied, generallyit is the fibrillated lyocell nanofibers that contribute to an increasedefficiency, while the PET nanofibers contribute to an increasedfiltration capacity. With higher basis weight, the filtration mediagenerally exhibits higher capacity due to increase in caliper, and thepore structure gets smaller and more compact due to more filtrationdepth. Therefore, using the very same two components, the fibrillatedlyocell nanofiber content must be decreased with an increase in basisweight in order to maintain the same efficiency level (which in thiscase, means that capacity will increase). With different grades (thatis, different CSF characteristics) of fibrillated lyocell nanofibers,the absolute amount of the fibers will vary greatly. For example, thedata show that substantially double the amount of the EFTec™ L200Lyocell nanofibers yields the same efficiency level as compared to theEFTec™ L010 Lyocell nanofibers. The data in general show that a minimumamount of about 2.5 wt. % EFTec™ L010 fibrillated Lyocell nanofiberswould be required while a maximum of 50 wt. % EFTec™ L200 fibrillatedLyocell nanofibers was required to achieve acceptable efficiencyperformance characteristics.

Example 5

Experimental glassfree media of this invention were grooved with thefollowing dimensions being achieved:

Commercial Glass Experimental Experimental Dimensions [mils] Media 7B13B SD Overall Caliper 38 38 39 SD Groove Depth 13 21 19 SD OpticalCaliper A 28 19 20

The table above shows that while the actual “flat” caliper of theexperimental media is much smaller than the “flat” caliper of thecommercial glass media, the same overall grooved caliper could beachieved by imparting a much larger groove. This means additional threedimensional filtration area is created, resulting in additionalfiltration performance in a converted filter. It was also observed thatother hand sheets embodying the present invention could be groovedwithout cracking at SD Groove Depths of up to 29 mils.

* * *

While the invention has been described in connection with what ispresently considered to be the most practical and preferred embodiment,it is to be understood that the invention is not to be limited to thedisclosed embodiment, but on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope thereof.

What is claimed is:
 1. A method of making filtration media comprising:(a) forming a wet laid sheet from a fibrous slurry comprised of a blendof synthetic non-fibrillated staple fibers and fibrillated cellulosicstaple fibers, and (b) drying the sheet to obtain the filtration media,wherein the fibrillated cellulosic fibers exhibit a Canadian StandardFreeness (CSF) of about 300 mL or less and are present in the filtrationmedia in an amount to achieve an overall filtration efficiency at 4microns of about 95% or higher and a ratio of filtration capacity tomedia caliper of 0.5 mg/in²/mils and greater.
 2. The method of claim 1,wherein the synthetic non-fibrillated staple fibers are formed of athermoplastic polymer selected from the group consisting of polyesters,polyalkylenes, polyacrylonitriles, and polyamides.
 3. The method ofclaim 1, wherein the synthetic non-fibrillated staple fibers arenon-fibrillated staple microfibers having an average fiber diameter ofless than about 10 microns and an average length of less than about 25millimeters.
 4. The method of claim 3, wherein the syntheticnon-fibrillated staple microfibers are polyethylene terephthalatemicrofibers.
 5. The method of claim 4, wherein the polyethyleneterephthalate microfibers are the water-washed residue of waternon-dispersible sulfopolyester fibers having a glass transitiontemperature (Tg) of at least 25° C., the sulfopolyester comprising (i)about 50 to about 96 mole % of one or more residues of isophthalic acidor terephthalic acid; (ii) about 4 to about 30 mole %, based on thetotal acid residues, of a residue of sodiosulfoisophthalic acid; (iii)one or more diol residues wherein at least 25 mole %, based on the totaldiol residues, is a poly(ethylene glycol) having a structureH—(OCH₂—CH₂)_(n)—OH, wherein n is an integer in the range of 2 to about500; and (iv) 0 to about 20 mole %, based on the total repeating unites,of residues of a branching monomer having 3 or more hydroxyl, and/orcarboxyl functional groups.
 6. The method of claim 1, wherein thesynthetic non-fibrillated staple fibers are present in an amount betweenabout 50 wt. % to about 99.5 wt. % ODW.
 7. The method of claim 1,wherein the fibrillated cellulosic staple fibers comprise fibrillatedlyocell nanofibers.
 8. The method of claim 7, wherein the fibrillatedlyocell nanofibers are present in an amount of between about 0.5 toabout 50 wt. % ODW.
 9. The method of claim 8, wherein the media has abasis weight of between about 15 gsm to about 300 gsm.
 10. The method ofclaim 1, wherein the synthetic staple fibers comprise polyethyleneterephthalate microfibers having an average fiber diameter of less thanabout 10 microns and an average length of less than about 25 millimeterswhich are present in an amount of between about 50 wt. % to about 99.5wt. % ODW, and wherein the fibrillated cellulosic staple fibers arepresent in an amount of at least about 0.5 to about 50 wt. % ODW. 11.The method of claim 1, wherein the fibrillated cellulosic fibers have anaverage diameter of about 1000 nanometers or less and an average lengthbetween about 1 mm to about 8 mm.
 12. The method of claim 1, furthercomprising blending natural wood pulp with the synthetic non-fibrillatedstaple fibers and fibrillated cellulosic staple fibers of the fibrousslurry.
 13. The method of claim 12, wherein the natural wood pulp ispresent in an amount of about 25 wt. % ODW or less.
 14. The method ofclaim 13, wherein the natural wood pulp is present in an amount of about20 wt. % ODW or less.
 15. The method of claim 1, further comprisingapplying at least one resin binder to the filtration media.
 16. Themethod of claim 15, wherein the resin binder is at least one selectedfrom the group consisting of styrene acrylic, acrylic, polyethylenevinyl chloride, styrene butadiene rubber, polystyrene acrylate,polyacrylates, polyvinyl chloride, polynitriles, polyvinyl acetate,polyvinyl alcohol derivates, starch polymers, epoxy, phenolics andcombinations thereof.
 17. The method of claim 15, wherein the resinbinder is present in an amount of between about 2 to about 50 wt. % SDC.18. The method of claim 1, which further comprises blending with thefibrous slurry at least one additive selected from the group consistingof wet strength additives, optical brighteners, fiber retention agents,colorants, fuel-water separation aides.
 19. The method of claim 1,further comprising forming longitudinally extending and latitudinallyseparated grooves in the filtration media.
 20. The method of claim 1,further comprising providing the filtration media as a first filtrationmedia layer, and laminating at least one additional second filtrationmedia layer to the first filtration media layer.
 21. The method of claim1, further comprising pleating the filtration media.
 22. The method ofclaim 21, further comprising co-pleating at least one supporting layerwith the filtration media.
 23. The method of claim 22, wherein thesupporting layer is a wire mesh layer.
 24. A method of making highefficiency and high capacity glass-free filtration media comprising: (a)forming a wet laid sheet from a fibrous slurry comprised of a blend ofsynthetic non-fibrillated staple microfibers and fibrillated cellulosicstaple fibers, wherein (i) the synthetic non-fibrillated staplemicrofibers have an average fiber diameter of less than about 10 micronsand an average fiber length of less than about 25 millimeters and areformed of a thermoplastic polymer selected from the group consisting ofpolyesters, polyalkylenes, polyacrylonitriles, and polyamides, andwherein (ii) the fibrillated cellulosic fibers exhibit a CanadianStandard Freeness (CSF) of about 300 mL or less and are present in themedia in an amount to achieve an overall filtration efficiency at 4microns of about 95% or higher and a ratio of filtration capacity tomedia caliper of 0.5 mg/in²/mils and greater; and (b) drying the sheetto obtain the filtration media.
 25. A method of making filtration mediacomprising: (a) forming a wet laid sheet from a fibrous slurry comprisedof a blend of synthetic non-fibrillated staple fibers and fibrillatedcellulosic staple fibers, and (b) drying the sheet to obtain thefiltration media, wherein the fibrillated cellulosic fibers are presentin the filtration media in an amount to achieve an overall filtrationefficiency at 4 microns of about 95% or higher and a ratio of filtrationcapacity to media caliper of 0.5 mg/in²/mils and greater, and whereinthe polyethylene terephthalate microfibers are the water-washed residueof water non-dispersible sulfopolyester fibers having a glass transitiontemperature (Tg) of at least 25° C., the sulfopolyester comprising (i)about 50 to about 96 mole % of one or more residues of isophthalic acidor terephthalic acid; (ii) about 4 to about 30 mole %, based on thetotal acid residues, of a residue of sodiosulfoisophthalic acid; (iii)one or more diol residues wherein at least 25 mole %, based on the totaldiol residues, is a poly(ethylene glycol) having a structureH—(OCH₂—CH₂)_(n)—OH, wherein n is an integer in the range of 2 to about500; and (iv) 0 to about 20 mole %, based on the total repeating unites,of residues of a branching monomer having 3 or more hydroxyl, and/orcarboxyl functional groups.